Dies used in a press machine include a top die fitted on a slide and a bottom die mounted on a bolster, between which a material may be pressed by a vertical stroke of the slide.
The vertical stroke of the slide is generally controlled with a slide guide such as depicted in FIGS. 6 and 7. Therein, a slide guide 61 (a plain-type guide) has sliding guide members between columns 62 and a slide 63, or a needle-roller type guide having needle roller 5 between the columns 62 and the slide 63. Slide guide 61 is arranged to guide the slide 63 at both upper and lower plural portions, such as at eight portions thereof. It is known that slide guide 61 is influenced by the dimensional change of the components of the press machine due to temperature changes or changes in the press operation, so that the slide guide 61 must have a minimum clearance.
Another slide guide 64 as shown in FIG. 7 comprises a slide 65 having downwardly extending guide posts 66 and a bed 67 provided with guide sleeves 68 into which the corresponding guide posts 66 may be inserted. There are four sets of guide posts 66 and the guide sleeves 68 with zero clearance. To allow the guiding operation to occur under conditions of dimensional change of the press machine, e.g., components due to temperature change as aforesaid, the diameter of guide post 66 is made short so as to decrease its rigidity and permit deflection.
The function of the slide guide where high precision pressing is necessary is to obtain accurate die registration. Another function of the slide guide is to keep the slide parallel to the bolster whenever the slide interacts with an eccentric upward load through the press operation. Therefore, the conventional slide guide 61 as shown in FIG. 6 may be expected to have enough strength to achieve precise pressing since the columns 62 have great rigidity even when the slide 63 interacts with an eccentric upward load during a press operation. However, since slide guide 61 has clearance, as aforesaid, the slide is likely to shift toward one side while pressing. Under such conditions, if the vertical stroke of the slide 63 is repeated or the top die does not coincide with the bottom die, the desirable precise press operation may not occur and the life expectancy of the dies may be shortened.
Since the slide guides 64 in FIG. 7 do not have clearance, precision work with the dies may be done reliably. However, because of the shortened diameter of the guide posts 66 as explained above, if the slide 65 interacts with an eccentric upward load during a press operation, the slide guide 64 may not work as well as expected.
The slide guide should be able to set the dies precisely as desired and also have enough rigidity under an eccentric load to continuously maintain the slide parallel to the bolster. However, conventional slide guides do not satisfy such conditions as described.
An object of the present invention is to obtain a high accuracy of setting of the dies and to have a slide guide with sufficient rigidity against an eccentric load so as to maintain the slide parallel to the bolster so that high accuracy of pressing materials in a press machine may be attained.